However, as this opportunity comes at the expense of practice time and the chance to work on car set-up for one of the race drivers, its value to the team must be considered carefully.
Similarly, in the 2004 Formula One season, BAR ran third driver Anthony Davidson and finished second in the World Constructors' Championship.
Starting with the 2007 season, the regulations were changed to their current form so that while a team could run a third driver during Friday practice, they were no longer allowed to provide them with a dedicated third car.
Third drivers are still used occasionally, most notably Sebastian Vettel drove for the BMW Sauber team on Fridays at the start of the 2007 season, Scottish driver Paul di Resta ran in eight Friday practice sessions for Force India during the 2010 season.
The International Race of Champions (IROC) employed former NASCAR drivers Dave Marcis, Dick Trickle and Jim Sauter as test drivers to prepare the setups for cars competing in the IROC series.